[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fiPFZZCb19_euJx8xNWLAuiw-TkTPEPldylEU6sR31mk":3},{"answer":4,"createTime":5,"id":6,"options":7,"origin":12,"question":19,"related":20,"source":30,"type":31},[],"2023-09-04 21:20:30",96237480,[8,9,10,11],"层次数据模型","网状数据模型","关系数据模型","面向对象数据模型",{"count":13,"courseId":14,"courseImg":15,"courseName":16,"workId":17,"workName":18},37,"ef292f84aa3a4a71ede6d3e4ee40c4eb","https:\u002F\u002Ftihai-oss-cloud.itihey.com\u002Fimg\u002Fe882b31f1b9df473ed78214ae95300cf.jpg","数据库系统","8be2ca7b8d0a4168a9a1703184557868","第2章章节测试","数据库技术的奠基人之一E.F.Codd从1970年起发表过多篇论文,主要论述的是( )",[21,32,35,44,53,62,72,81,90,96],{"answer":22,"createTime":5,"id":23,"options":24,"question":29,"source":30,"type":31},[],96237479,[25,26,27,28],"层次结构","二维表结构","网状结构","封装结构","在数据库设计中用关系模型来表示实体和实体之间的联系.关系模型的结构是( )","v1",0,{"answer":33,"createTime":5,"id":6,"options":34,"question":19,"source":30,"type":31},[],[8,9,10,11],{"answer":36,"createTime":5,"id":37,"options":38,"question":43,"source":30,"type":31},[],96237481,[39,40,41,42],"可以由多个任意属性组成","至多由一个属性组成","由一个或多个属性组成,其值能够惟一标识关系中一个元组","以上都不是","关系模型中,一个候选码是( )",{"answer":45,"createTime":5,"id":46,"options":47,"question":52,"source":30,"type":31},[],96237482,[48,49,50,51],"候选码","外码","超码","主码","一个关系只有一个( )",{"answer":54,"createTime":5,"id":55,"options":56,"question":61,"source":30,"type":31},[],96237483,[57,58,59,60],"同一关系模式下,可有很多的关系","关系模式是关系的结构, 关系是关系模式在某一时刻的数据","关系模式是稳定的;而关系是某一时刻的值,是随时间可能变化的","以上3项都正确","以下对关系模式和关系的描述中正确的是()",{"answer":63,"createTime":64,"id":65,"options":66,"question":71,"source":30,"type":31},[],"2023-09-04 21:20:31",96237484,[67,68,69,70],"关系数据结构、关系操作集合和关系规范化理论","关系数据结构、关系规范化理论和关系完整性约束","关系操作集合、关系规范化理论和关系完整性约束","关系数据结构、关系操作集合和关系完整性约束","关系数据模型的三个要素是()",{"answer":73,"createTime":64,"id":74,"options":75,"question":80,"source":30,"type":31},[],96237485,[76,77,78,79],"属性","关系","域","元组","下列关于关系数据模型的术语中,哪一个术语所表达的概念与二维表中的"行"的概念最接近?()",{"answer":82,"createTime":64,"id":83,"options":84,"question":89,"source":30,"type":31},[],96237486,[85,86,87,88],"R(A)","R(A,B,C,D)","R(A*B*C*D)","R(A,B)","设有属性A,B,C,D,以下表示中不是关系的是()",{"answer":91,"createTime":64,"id":92,"options":93,"question":95,"source":30,"type":31},[],96237487,[77,94,79,78],"分量","一组具有相同数据类型的值的集合称为()",{"answer":97,"createTime":64,"id":98,"options":99,"question":104,"source":30,"type":31},[],96237488,[100,101,102,103],"9","24","14","10","设D1、D2和D3定义域中的基数分别为2、3和4,则D1xD2xD3的元组数为( )"]